This invention relates to data transmission systems between a plurality of central processing units (CPU's).
The data transmission system of the type referred to is effective to be used for the data transmission between the respective CPU's incorporated in a key telephone system.
In general, the key telephone system must process various sorts of signals in a short time. To satisfy such demand, the system is so arranged that constituent hardwares are installed on a plurality of boards as divided according to their function respectively with a main CPU or a sub-CPU.
The conventional data transmission system, however, has been defective specifically in that latch and buffer stages must be provided to the respective boards which carry, in particular, the sub-CPU, so that the number of required components will have to be thereby increased. This renders the system to be expensive, and fails to minimize installation space. Furthermore, the system requires a plurality of command control lines, which disadvantageously involves a large wiring space and troublesome wiring work.